Friction transmission belts with a pulley contacting portion made of a rubber composition containing EPDM (ethylene-propylene-diene monomer) as a rubber component have been known.
Japanese Unexamined Patent Publication No. 2006-300149 discloses a V-ribbed belt in which a compressed rubber layer as a pulley contacting portion is made of a rubber composition containing an EPDM mixture as a rubber component. The EPDM mixture includes an EPDM with an ethylene content of 40% by mass or more and 59% by mass or less, and an EPDM with an ethylene content of 68% by mass or more and 90% by mass or less.
Japanese Unexamined Patent Publication No. 2002-081506 discloses a V-ribbed belt in which a compressed rubber layer as a pulley contacting portion is made of a rubber composition containing an EPDM mixture as a rubber component. The EPDM mixture includes: 7% by mass or more and 12% by mass or less of a high molecular weight EPDM component in which the molecular weight is 106 or more and the ethylene content is 65% by mass or more; and 26% by mass or more and 60% by mass or less of a low molecular weight EPDM component in which the molecular weight is 105 or less and the ethylene content is 60% by mass or less.
Re-publication of PCT International Publication No. 2010/047029 discloses a flat belt in which a rubber layer as a pulley contacting portion of a belt body is made of a rubber composition containing an EPDM mixture as a rubber component. The EPDM mixture includes an EPDM with an ethylene content of 70% or 85%, and an EPDM with an ethylene content of 52%.
Re-publication of PCT International Publication No. 2007/018148 discloses a V-ribbed belt in which a compressed rubber layer as a pulley contacting portion is made of a rubber composition containing an EPDM mixture as a rubber component. The EPDM mixture includes an EPDM with an ethylene content of 70% and an EPDM with an ethylene content of 50%.